System, protocol and associated methods for wireless multimedia distribution

ABSTRACT

A system, protocol and associated methods for wireless multimedia distribution are generally described herein.

TECHNICAL FIELD

Embodiments of the invention are generally directed to wirelesscommunication systems and, more particularly, to a system, protocol andassociated methods for wireless multimedia distribution.

BACKGROUND

Wireless communication channels are inherently lossy, i.e., there is acertain amount of information that once transmitted will be lost duringtransmission and/or receive processing of the wireless communicationchannel. Left unattended, this lost information (sometimes referred toas frames, packets, symbols, bits, etc., cumulatively referenced hereinas datagrams) may well rise to the level where the amount of lostinformation has an adverse effect on the performance of the receivingdevice and/or associated application. In multimedia applicationssupporting the communication of audio, video, data or combinationsthereof, this is especially true as information lost during wirelesscommunication transmission may well result in a diminished userexperience.

In a unicast communication environment, wherein a single sourcecommunicates with a single destination, media content lost due todropped datagrams may be recoverable using conventional forward errorcorrection and/or re-transmission techniques. Unfortunately, suchconventional techniques are not readily adapted to a multicast, or pointto multi-point communication environment.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not by way of limitation, in the figures of the accompanyingdrawings in which like reference numerals refer to similar elements andin which:

FIG. 1 is a block diagram of an example communication system withinwhich embodiments of the invention may be practiced;

FIG. 2 is a block diagram of an example content delivery system,according to one example embodiment;

FIG. 3 is a flow chart of an example method for providing multimediacontent within a wireless communication system, according to but oneembodiment;

FIG. 4 is a graphical representation of a communication flow diagram forproviding multimedia content within a wireless communication system,according to one embodiment; and

FIG. 5 is a block diagram of an example article of manufacture includingcontent which, when executed by an accessing machine, causes the machineto implement one or more aspects of embodiment(s) of the invention.

DETAILED DESCRIPTION

Embodiments of a system, protocol and associated methods to providemultimedia content via a wireless communication system are generallypresented. More specifically, a system, protocol and associated methodsare disclosed herein that improve the reliability of a wirelessmulticast transmission of multimedia content (audio, video, data or anycombination thereof) to one or more devices.

This improvement is achieved by recognizing that the distribution ofmedia content typically consumes about one megabyte per second (1 Mb/s),while a wireless communication channel typically provides a physicalbandwidth of between 2 and 54 Mb/s (e.g., in wireless local area network(WLAN) applications). To effectively utilize the heretoforeunderutilized bandwidth of the wireless communication channel to improvethe reliability of a multicast transmission, a reliable multicast agent(RMA) is introduced herein.

As developed more fully below, an RMA introduced in the transmitter andreceiver of a multicast channel will manage multicast communication andwhen dropped (or, unrecoverable) datagrams are detected, a secondarycommunication channel is dynamically established between the transmitterand affected receiver. According to one embodiment, the RMA establishesthe secondary communication channel as a “virtual” channel within thepreviously underutilized bandwidth of the physical communicationchannel. According to one embodiment, the virtual channel is a unicastchannel. The RMA may then selectively retransmit the dropped datagramsto the source via the secondary communication channel.

According to one embodiment, this secondary communication channel isimplemented at the media access control (MAC) layer of the communicationprotocol stack in the source transmitter and the destination receiver,thereby offloading this responsibility from higher layers, e.g., theapplication layer. In this regard, the RMA disclosed herein may beimplemented in support of legacy multimedia processing applications,thereby improving the perceived quality and reliability of suchapplications without a commensurate, costly upgrade of suchapplications.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily all referring to the sameembodiment. Furthermore, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Example Communications Environment

FIG. 1 illustrates a block diagram of an example wireless communicationenvironment 100 within which embodiments of the invention may well bepracticed. More particularly, FIG. 1 is depicted comprising one or moreof a media content resource (e.g., a media delivery server) 102, and aplurality of wireless communication devices 104 and 106A . . . N, eachcoupled as depicted. According to one example embodiment, the contentresource 102 provides media content to a first communication device 104for wireless, multicast distribution to two or more remote communicationdevices 106A . . . N. According to one example embodiment, the wirelesscommunications element (104-108) of environment 100 may be, withoutlimitation, a wireless local area network (WLAN), wireless metropolitanarea network (WMAN), a wireless personal area network (WPAN), a directbroadcast satellite (DBS) system and the like, although the invention isnot limited in this regard.

For purposes of illustration, and not limitation, the wirelesscommunication element (104-108) will be developed more fully in thecontext of an example WLAN implementation, although the invention is notlimited in this regard. In accordance with such an exampleimplementation, the WLAN distribution system may include an access point(AP) 104 communicatively coupled to one or more client stations (STA)106A . . . N through one or more instances of a WLAN communicationchannel 108A . . . N. In this regard, WLAN distribution system 104-108may operate in accordance with any one or more of the IEEE 802.11 and/or802.16 communication standards¹, implementing an associated protocol,although the invention is not limited in this regard.¹See, e.g., the IEEE 802.11, 1999 Edition; Information TechnologyTelecommunications and Information Exchange Between Systems—Local andMetropolitan Area Networks—Specific Requirements, Part 11: WLAN MediumAccess Control (MAC) and Physical (PHY) Layer Specifications, itsprogeny and supplements thereto (e.g., 802.11a, .11g and .11n); see alsothe IEEE Std 802.16-2001 IEEE Std. 802.16-2001 IEEE Standard for Localand Metropolitan area networks Part 16: Air Interface for FixedBroadband Wireless Access Systems, its progeny and supplements thereto(e.g., 802.16a, .16d, and .16e).

According to one example embodiment, device 104 and one or more ofdevices 106A . . . N may include the reliable multicast agent (RMA) (notparticularly denoted in this view) introduced above. An RMA implementedin a transmitter-receiver pair may detect that some subset of thecontent initially sent via the multicast channel was lost intransmission, or is otherwise unrecoverable at the receiver. Inresponse, the RMA may then coordinate the selective retransmission ofthe identified content to the select receiver(s) that would otherwise belost in the multicast communication channel. Rather than retransmittingthe content via the multicast channel, perhaps impairing the perceivedquality of that communication channel, the RMA coordinates the selectiveretransmission via a dynamically established, secondary communicationchannel.

According to one embodiment, the secondary communication channel is a“virtual” unicast communication channel between the transmitter and theselect receiver(s), although the scope of the invention is not limitedin this regard. As used herein, the term virtual is intended to denotethat a separate and distinct channel is established within a commonphysical channel. That is, the physical channel supports the multicastcommunication channel as well as the unicast, secondary channel.

According to one embodiment, the RMA coordinates buffering contentreceived via the multicast channel and the secondary communicationchannel for promotion to a media processing application, ensuring thatthe media content is delivered to the application in the propersequence, although the invention is not limited in this regard.

But for the selective inclusion of RMA and/or elements thereof, thedevices 102-106 of communication environment 100 are intended torepresent any of a wide range of electronic devices known in the art. Inthis regard, communication networks of greater or lesser complexity thatnonetheless include the teachings of the RMA disclosed herein areintended to be captured by the scope and spirit of the claims, below.

Example Architecture(s)

Turning to FIG. 2, a block diagram of an example communicationenvironment 200 is depicted through which multimedia content may bedelivered according to embodiments of the invention. In accordance withthe illustrated example embodiment of FIG. 2, communication environment200 is depicted comprising one or more of a content resource 202 coupledto a wireless communication network 203 including at least a firstwireless communication device 204 and a second wireless communicationdevice 206, each coupled as depicted. For ease of illustration, and notlimitation, the wireless communication network 203 of FIG. 2 merelydepicts two devices, 204 and 206, engaged via a multicast communicationchannel 108, although the scope of the invention is not limited in thisregard. As introduced above, wireless communication network 203 isintended to represent any of a wide range of wireless communicationnetworks and associated protocols through which a multicast distributionchannel may be established.

According to one embodiment, consistent with the example WLANimplementation of FIG. 1, the wireless communication network 203 may beutilized to distribute multimedia content received from a contentresource 202 to one or more devices (e.g., 206) via a multicastcommunication channel 108. In this regard, content resource 202 mayinclude an application 208 to provide media content to requestingdevices, e.g., via a wireline communication medium, although the scopeof the invention is not limited in this regard.

Device 204 is depicted comprising one or more of RMA(s) 210, beaconmanager(s) 212 and buffer(s) 214, each logically coupled as depicted.According to one example embodiment consistent with the example WLANimplementation introduced above, device 204 may be an access point (AP)of wireless communication network 203, although the invention is notlimited in this regard. According to one example embodiment, device 204may be a block diagram representation of device 104.

According to one embodiment, RMA 210 may perform one or more managementfunctions associated with the multicast distribution of media content(again, audio, video, data or any combination thereof). According to oneembodiment, RMA 210 may be implemented as a feature in the media accesscontrol (MAC) layer of a wireless network interface (e.g., atransceiver), although the invention is not limited in this respect. Inthis regard, RMA 210 may control the flow of media content to thewireless multicast channel for transmission via the physical channel. Asdiscussed below, RMA 210 may fragment, or parse, media content receivedin buffer 214 from content resource 202.

RMA 210 may then control reading of the media fragments from the buffer214 to the multicast communication channel 108 for transmission to theremote wireless devices (e.g., 206). According to one embodiment, RMA210 may generate a multicast announcement, which is passed to beaconmanager 212 for inclusion as an information element in one or morebeacons 224. According to one embodiment, the multicast announcementincludes one or more of a destination addresses and sequence numbers ofthe buffered frames for each address, and a copy of the multicastannouncement sent in a prior beacon (to enable retransmission to devicesthat may have missed the last beacon), although the invention is notlimited in this regard.

According to one embodiment, as RMA 210 is reading media fragments outof the buffer for transmission via the multicast communication channel,it marks (e.g., via a header or other mechanism) the relative positionof each fragment within a broader sequence of the content. In thisregard, each fragment may be denoted by a sequence number, although theinvention is not limited in this regard.

According to one embodiment, RMA 210 works in conjunction with a beaconmanager 212 to manage and monitor the quality of the multicasttransmission channel 108. Beacon manager 212 may function under thecontrol of, or is integrated within RMA 210, although the invention isnot limited as such. According to one embodiment, prior to orconcurrently with the multicast transmission of one or more mediafragments read from buffer 214, beacon manager 212 may issue a beaconsignal 224 to devices within its coverage area of the wireless network203. The beacons 224 may include one or more of source information,destination information and/or the sequence numbers of the fragmentsincluded within a current transmission window (e.g., bounded by time,bandwidth, space, etc.).

Device 206 is depicted comprising a complementary set of one or more ofRMA(s) 210, beacon manager(s) 216, buffer(s) 218, each logically coupledas depicted. Consistent with an example WLAN implementation introducedabove, device 206 may be a station (STA) within wireless communicationnetwork 203, although the scope of the invention is not so limited.According to one example embodiment, device 206 may be a block diagramrepresentation of one or more of devices 106A . . . N.

According to one embodiment, device 206 may also include a destinationapplication 220, to receive the content sourced from content resource202. According to one embodiment, application(s) 220 may be a mediaplayer to render multimedia content for the enjoyment of an end-user ofdevice 206, although the scope of the invention is not limited to suchan implementation.

As above, RMA 210 in a receiving device (e.g., 206) may performoperations/functions that are complementary to that of the transmittingRMA 210 (e.g., in device 204). In this regard, beacon manager 216 mayreceive and decode beacons 224 to recover one or more of sourceinformation, destination information and/or sequence number information,at least a subset of which is provided to RMA 210. The sequence numberinformation provides a listing of media fragments that have been sent bythe transmitting device (204) and should be contained within the receivebuffer 218.

) RMA 210 of device 206 may monitor the media fragments populatingbuffer 218, and confirms that the sequence numbers match those receivedvia the beacons 224. According to one embodiment, RMA 210 of device 206may monitor the sequence numbers of the information (e.g., mediafragments) as they are written into buffer 218. Alternatively, RMA 210of device 206 may interrogate buffer 218 to identify the sequencenumbers of the information stored therein, or may monitor theinformation as it is read out of the buffer, although the invention isnot limited in this regard. Accordingly, RMA 210 of device 206 maycompare the sequence numbers of the information received via themulticast channel 108 against the sequence numbers received in thebeacons 224 to identify dropped/unrecoverable information.

According to one embodiment, RMA 210 and/or beacon manager 216 willbuffer at least a subset of the information received via the beaconsduring the transmission window, or until the information associated withthe sequence numbers embedded within the received beacons 224 isconfirmed received. As introduced above, the transmission window may bedefined in time, space, bandwidth, etc., although the invention is notso limited. If information associated with one or more sequence numbersembedded within the received beacons 224 are not confirmed as receivedeither before they are needed (e.g., by application 220), or by theexpiration of the transmission window, RMA 210 in device 206 may issue aretransmission request to RMA 210 in the source device (204). Accordingto one embodiment, the retransmission request includes a list of one ormore sequence numbers requested for retransmission.

According to one embodiment, upon receiving a retransmission request,RMA 210 may establish a secondary communication channel 222 throughwhich to retransmit the information associated with the sequencenumber(s) provided in the retransmission request. As introduced above,the secondary communication channel 222 may be a virtual, unicastcommunication channel (i.e., particularly denoting the destinationaddress of the requesting device). According to one example embodiment,the unicast communication channel supplements the multicastcommunication channel 108 with retransmitted information that wouldotherwise be lost during transmission via the multicast channel 108, orduring receive processing at the destination device (206). Unlike themulticast communication channel, the retransmission content in thesecondary communication channel 222 may include a destination identifierassociated with but a single device (e.g., a requesting device 206),although the invention is not so limited. More particularly, RMA 210 indevice 204 reads the requested information (denoted by sequence number)out of buffer 214 (if still available) for retransmission via thesecondary communication channel 222.

According to one embodiment, the RMA 210 may be implemented as a featureof the MAC. In this regard, RMA 210 may well be implemented in hardware,software, firmware, or any combination thereof without limitation.According to one embodiment, RMA 210 is implemented within a wirelesscommunication chipset, although the invention is not limited in thisregard.

Although not particularly denoted, those skilled in the art willappreciate that the devices (e.g., 204, 206) of the wirelesscommunication network 203 may also include wireless transmitter andwireless receiver (cumulatively, transceiver) capability to effect thewireless communication link in accordance with one or more wirelesscommunication protocols introduced above. But for the introduction ofthe RMA functionality and features disclosed herein, any of a range oftransmitter and receiver architectures may well be used in accordancewith the teachings of the present invention. In addition to thetransceiver functionality (not particularly denoted), devices (e.g.,204, 206) of the wireless communication network 203 may include one ormore antenna(e) such as, e.g., substantially omnidirectional antenna(e),directional antenna(e), and the like.

Having introduced the operating environment and logical relationshipbetween various elements of the system in FIGS. 1 and 2, attention isnow directed to FIG. 3, where an example method for the reliablemulticast of content using RMA 210 is described, according to but oneembodiment.

Example Operation

With continued reference to FIGS. 1 and 2, an example method forreliable wireless multicast communication is generally presented withreference to FIG. 3, according to but one example embodiment.

In accordance with the illustrated example embodiment of FIG. 3, themethod begins with block 302 where one or more device(s) (e.g., 104,106A . . . N) within a wireless communication network perform deviceassociation. According to one example embodiment, at least a subset ofdevices (204, 206) within the communication network exchange informationdenoting device capability including, for example, whether theparticular device(s) include RMA capability.

In block 304 a multicasting session may begin. According to oneembodiment, the multicasting session may begin during or subsequent tothe association phase. According to one embodiment, content is sourcedfrom a content resource, e.g., media server 202 via application 208, toa wireless transmitter of the multicast channel, e.g., device 204.

As introduced above, an RMA 210 in device 204 may fragment the contentfor transmission via the multicast communication channel 108 to one ormore remote devices (e.g., 206). Such multicast transmission continues,block 308) until an RMA 210 (e.g., in a receiving device) detects theloss of informational content, block 306. As above, the lost content maybe detected by the identification of missing sequence numbers associatedwith the received content.

If RMA 210 detects lost content it may cause a retransmission request tobe issued, block 306. According to one embodiment, the retransmissionrequest is a MAC layer message transmit from the receiving device 206 tothe source of the multicast communication channel 108, device 204.

In response to the retransmission request, RMA 210 in device 204dynamically establishes a secondary, retransmission channel 222 with therequesting device 206, block 310. As introduced above, RMA 210 in device204 may read informational content from buffer 214 associated with therequested sequence numbers. The read informational content is formattedby RMA 210 in device 204 into unicast data packets for transmission viathe secondary communication channel 222 to the requesting device 206.According to one example embodiment the secondary communication channel222 is a virtual channel, utilizing un(der)-utilized bandwidth of aphysical wireless communication link supporting the multicastcommunication channel 108.

In block 310, RMA 210 in device 204 may retransmit the requested contentvia the secondary communication channel 222. According to oneembodiment, RMA 210 in device 204 may support several secondarycommunication channel(s) with disparate receiving device(s) (e.g., 206)while continuing to support multicast communication via the multicastcommunication channel. Upon receiving the missing frames, RMA 210 in thereceiving device 206 may reorder the fragments to achieve proper order,e.g., according to sequence number.

Turning briefly to FIG. 4, a communication flow diagram 400 of anexample implementation of the RMA 210 is provided, according to oneexample embodiment. As shown, the communication flow diagram 400 isgenerally divided into two sections, or phases: an association phase 402and a multicast phase 404, although the invention is not limited in thisregard. For ease of explanation, and not limitation, the communicationflow diagram will be developed within the context of an example WLANcommunication environment.

As introduced above, during the association phase 402 (block 302 of FIG.3), an access point 204 issues a beacon 406 to one or more remotedevices (e.g., 206). According to one aspect of the invention, RMA 210in device 204 may generate a multicast announcement that is forwarded toa beacon manager 212. Beacon manager 212 then generates a beacon messagefor transmission to the remote stations. As introduced above, thebeacons 406 may include an information element denoting that device 204supports RMA retransmission capability.

In response to receipt of the beacon(s) 406, one or more of themulticast target device(s) (e.g., 206) issues an association request408. As above, the RMA 210 receives at least a subset of theinformational content received via beacon manager 216, and thengenerates the response 408. According to one embodiment, the response408 includes an information element denoting that device 206 supportsRMA retransmission capability.

Device 204 receives the association request 408, whereupon at least asubset of the content of the request 408 is passed to RMA 210. Inresponse, RMA 210 in device 204 generates an association response 410denoting that retransmission is enabled as between the two devices 204,206.

During or subsequent to the association phase 402, the content resource202 may begin transmitting content 412 a . . . n to device 204. Asprovided above, the communication medium between the content resource202 and device 204 may well be one or more of a wired communicationmedium, a wireless communication medium and/or an optical communicationmedium and may actually traverse many different networks between suchdevices.

As introduced above, RMA 210 in device 204 may generate a multicastannouncement for transmission in one or more beacons by beacon manager212. RMA 210 in device 204 begins to parse, or fragment the receivedmedia content as it is read into buffer 218. According to oneembodiment, RMA 210 may initialize a buffer validity timer to track the“age” of the contents in the buffer. According to one embodiment, thebuffer may be flushed after the timer expires to make room for newcontent, although the invention is not limited in this respect.

Once beacon manager 214 receives the multicast announcement from RMA210, it generates a beacon 414 for transmission to the remote devicesinitiating the multicast session. According to one embodiment, thebeacon 414 may include one or more of a source address, destinationaddress(es), and sequence number(s) of the content to be delivered viathe multicast channel(s).

Commensurate with or subsequent to transmission of beacon 414, RMA 210of device 204 initiates multicast transmission of media content via themulticast channel 416. According to one embodiment, the content istransmitted on a frame-by-frame basis (where the fragment size is aframe) in a sequential fashion, although the invention is not limited inthis regard.

Multicast transmission continues until a lost frame 418 is identified.As introduced above, the identification of the lost frame may arise byreceiving another multicast fragment 420 out of order, or failing toreceive a multicast fragment 418 within a multicast transmission window,e.g., defined by time, space, bandwidth, etc., or the receipt of asubsequent beacon 422.

In response, RMA 210 in device 206 may generate and issue aretransmission request 424. As provided above, the retransmissionrequest 424 may include one or more of the address of the requestingentity, the address of the source device (204) and/or the sequencenumber (e.g., 2) associated with the lost information.

In response to receiving a retransmission request, RMA 210 in device 204may establish a secondary communication channel 426 through which totransmit the requested information (e.g., associated with sequencenumber 2). More particularly, RMA 210 attempts to identify the requestedinformation (Seq. No. 2) in buffer 214 for retransmission. Assuming thebuffer validity timer has not yet expired, causing the buffer to beflushed, RMA 210 in device 204 generates a unicast frame 426 fortransmission to device 206. As introduced above, retransmission via thesecondary communication channel 426 may occur simultaneously withcontinued multicast 428 and beacon 430 communication traffic, althoughthe scope of the invention is not limited in this regard.

By providing support for an alternate, reliable means of retransmittinginformational content that would otherwise be lost to, or unrecoverablefrom the lossy wireless communication channel supporting the multicastdistribution of such media content, the RMA may significantly improvethe user experience associated with wireless communication applications.

Alternate Embodiment(s)

FIG. 5 illustrates a block diagram of an example storage mediumcomprising content which, when invoked, may cause an accessing machineto implement one or more aspects of the RMA 210 and/or associatedmethods 300, 400. In this regard, storage medium 500 may include content502 (e.g., instructions, data, or any combination thereof) which, whenexecuted, causes an accessing appliance to implement one or more aspectsof the RMA 210 described above.

The machine-readable (storage) medium 500 may include, but is notlimited to, floppy diskettes, optical disks, CD-ROMs, andmagneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnet or opticalcards, flash memory, or other type of media/machine-readable mediumsuitable for storing electronic instructions. Moreover, the presentinvention may also be downloaded as a computer program product, whereinthe program may be transferred from a remote computer to a requestingcomputer by way of data signals embodied in a carrier wave or otherpropagation medium via a communication link (e.g., a modem, radio ornetwork connection). As used herein, all of such media is broadlyconsidered storage media.

It should be understood that embodiments of the present invention may beused in a variety of applications. Although the present invention is notlimited in this respect, the circuits disclosed herein may be used inmany apparatuses such as in the transmitters and receivers of a radiosystem. Radio systems intended to be included within the scope of thepresent invention include, by way of example only, wireless local areanetworks (WLAN) devices and wireless wide area network (WWAN) devicesincluding wireless network interface devices and network interface cards(NICs), base stations, access points (APs), gateways, bridges, hubs,cellular radiotelephone communication systems, satellite communicationsystems, two-way radio communication systems, one-way pagers, two-waypagers, personal communication systems (PCS), personal computers (PCs),personal digital assistants (PDAs), sensor networks, personal areanetworks (PANs) and the like, although the scope of the invention is notlimited in this respect. Such devices may well be employed within any ofa variety of

Embodiments of the present invention may also be included in integratedcircuit blocks referred to as core memory, cache memory, or other typesof memory that store electronic instructions to be executed by themicroprocessor or store data that may be used in arithmetic operations.In general, an embodiment using multistage domino logic in accordancewith the claimed subject matter may provide a benefit tomicroprocessors, and in particular, may be incorporated into an addressdecoder for a memory device. Note that the embodiments may be integratedinto radio systems or hand-held portable devices, especially whendevices depend on reduced power consumption. Thus, laptop computers,cellular radiotelephone communication systems, two-way radiocommunication systems, one-way pagers, two-way pagers, personalcommunication systems (PCS), personal digital assistants (PDA's),cameras and other products are intended to be included within the scopeof the present invention.

The present invention includes various operations. The operations of thepresent invention may be performed by hardware components, or may beembodied in machine-executable content (e.g., instructions), which maybe used to cause a general-purpose or special-purpose processor or logiccircuits programmed with the instructions to perform the operations.Alternatively, the operations may be performed by a combination ofhardware and software. Moreover, although the invention has beendescribed in the context of a computing appliance, those skilled in theart will appreciate that such functionality may well be embodied in anyof number of alternate embodiments such as, for example, integratedwithin a communication appliance (e.g., a cellular telephone).

In the description above, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however, toone skilled in the art that the present invention may be practicedwithout some of these specific details. In other instances, well-knownstructures and devices are shown in block diagram form. Any number ofvariations of the inventive concept are anticipated within the scope andspirit of the present invention. In this regard, the particularillustrated example embodiments are not provided to limit the inventionbut merely to illustrate it. Thus, the scope of the present invention isnot to be determined by the specific examples provided above but only bythe plain language of the following claims.

1. A method comprising: transmitting informational content to one ormore remote devices through a multicast communication channel over awireless communication link; and selectively retransmitting some subsetof the informational content to a subset of the one or more remotedevices through a unicast communication channel over the wirelesscommunication link upon request.
 2. A method according to claim 1,further comprising: receiving the informational content and parsing itinto two or more fragments, each fragment denoted by a sequence number.3. A method according to claim 2, further comprising: generating amulticast announcement for transmission to the one or more remotedevices through a beacon over the wireless communication link, themulticast announcement including sequence number information associatedwith upcoming multicast transmissions.
 4. A method according to claim 3,further comprising: receiving a retransmission request from a devicedenoting a failure to receive at least a subset of the informationalcontent transmitted via the multicast communication channel.
 5. A methodaccording to claim 4, wherein the retransmission request includes one ormore sequence number(s) associated with the subset of the informationalcontent.
 6. A method according to claim 5, further comprising:generating a message for transmission via the unicast communicationchannel by reading one or more informational fragment(s) from the bufferassociated with the requested sequence number(s).
 7. A storage mediumcomprising content which, when executed causes an accessing device toimplement a method according to claim
 1. 8. A device comprising: areliable multicast agent (RMA), to transmit informational content to oneor more remote devices through a multicast communication channel over awireless communication link, and to selectively retransmit some subsetof the informational content to a subset of the one or more remotedevices through a unicast communication channel over the wirelesscommunication link upon request.
 9. A device according to claim 8, theRMA to receive the informational content and parse it into two or morefragments, each fragment denoted by a sequence number for storage in abuffer.
 10. A device according to claim 9, wherein the RMA generates amulticast announcement for transmission to the one or more remotedevices through a beacon over the wireless communication link, themulticast announcement including sequence number information associatedwith upcoming multicast transmissions.
 11. A device according to claim10, the RMA to receive a retransmission request from a device denoting afailure to receive at least a subset of the informational contenttransmitted via the multicast communication channel.
 12. A deviceaccording to claim 11, wherein the retransmission request includes oneor more sequence number(s) associated with the subset of theinformational content.
 13. A device according to claim 12, the RMA togenerate a message for transmission via the unicast communicationchannel by reading one or more informational fragment(s) from the bufferassociated with the requested sequence number(s).
 14. A device accordingto claim 8, further comprising: a wireless transceiver, responsive tothe RMA, through which the wireless communication link between thedevice and a remote device.
 15. A device according to claim 14, furthercomprising: One or more substantially omnidirectional antenna(e),responsive to the wireless transceiver, to support transmission andreception of the wireless communication link.
 16. A system comprising: areliable multicast agent (RMA), to transmit informational content to oneor more remote devices through a multicast communication channel over awireless communication link, and to selectively retransmit some subsetof the informational content to a subset of the one or more remotedevices through a unicast communication channel over the wirelesscommunication link upon request; and one or more substantiallyomnidirectional antenna(e), through which the RMA may establish themulticast communication channel and the unicast communication channelover the wireless communication link with the remote device(s).
 17. Asystem according to claim 16, the RMA to receive the informationalcontent and parse it into two or more fragments, each fragment denotedby a sequence number for storage in a buffer.
 18. A system according toclaim 17, wherein the RMA generates a multicast announcement fortransmission to the one or more remote devices through a beacon over thewireless communication link, the multicast announcement includingsequence number information associated with upcoming multicasttransmissions.
 19. A system according to claim 18, the RMA to receive aretransmission request from a device denoting a failure to receive atleast a subset of the informational content transmitted via themulticast communication channel.
 20. A system according to claim 19,wherein the retransmission request includes one or more sequencenumber(s) associated with the subset of the informational content.
 21. Asystem according to claim 20, the RMA to generate a message fortransmission via the unicast communication channel by reading one ormore informational fragment(s) from the buffer associated with therequested sequence number(s).